A telephone number is a sequence of digital digits (0-9) that is used for identifying a destination telephone in a telephone network. Most telephones are interconnected via a conventional public switched telephone network (PSTN), where the format of telephone numbers is standardized by the International Telecommunication Union (ITU). In the past, businesses had a single telephone number for a main switchboard, with a switchboard operator connecting callers to various individuals within that business. In cases where the called party did not answer, the caller was typically transferred back to the main switchboard.
Today, with the widespread use of voicemail and other advanced communication technologies, many enterprises use Direct Inbound Dialing (DID) lines so that an outside caller may call directly to a person within a business. Often times, the DID number uses a pattern from the called party's telephone internal extension, e.g., where the last three or four digits symbolize the called person's (“callee's”) extension.
A private telephone network known as a private branch exchange (PBX) is commonly used within many enterprises. In a PBX, users in a business organization share a certain number of outside lines. A general description of PBX systems and a combined computer telephone integration (CTI) and PBX system that enables custom telephone features for multi-function telephone sets (MTS) located in a hotel room is disclosed in U.S. Pat. No. 6,798,874. An IP conference telephone system compatible with IP-PBX systems is disclosed in U.S. Pat. No. 6,654,455.
In certain PBX systems, a small number of telephones may be shared among a large number of employees to reduce equipment costs and expenses. For example, large retail stores with dozens of sales representatives, industrial laboratories, and large manufacturing centers with hundreds of factory floor workers, may arrange their workplace so as to have a limited number of phone devices distributed about the building for general use among the employees. Each employee is typically assigned a unique extension number. Callers to a main business number may be prompted by an interactive voice response (IVR) system to enter the extension of the person with whom they wish to speak. In many cases, incoming calls to all extension numbers are routed through the PBX system to the commonly shared telephone devices.
The problem with these prior art systems, however, is that any worker with access to the shared telephone devices may answer any call to any extension number. Thus, sharing telephone equipment with others—while reducing equipment costs and expenses—does come at the price of potentially comprising the privacy of the caller and/or callee.
A variety of different, specific solutions to the problem of telephone privacy have been proposed. One simple approach, for example, is taught in U.S. Pat. No. 6,917,672, which teaches identifying parties to a call so that a third party authority—which may include a business, a parent, a court, or some other authority—can regulate calls according to caller and callee pairs. U.S. Pat. No. 6,912,275 teaches a telephone answering system that provides security for a voicemail message platform through the use of a one-time password process. Additionally, U.S. Pat. No. 6,918,034 discloses a method and apparatus to provide encryption and authentication of a mini-packet in a multiplexed real-time protocol (RTP) payload transported across an IP telephony network.
Despite past efforts aimed at ensuring call privacy in the business enterprise environment, there still remains an unsatisfied need for a mechanism that allows sharing of telephone devices for receiving incoming calls without compromising call privacy.